Mobile multi-hop broadcast packet radio networks are known for rapid and convenient deployment, self organization, mobility, and survivability. Such a network is illustrated in FIG. 1. A transmission from one node, from node N1 of FIG. 1 for example, is broadcast to all nodes in its “neighborhood”. Ultra-high frequency (UHF) systems generally have a neighborhood defined by nodes located within line of sight of the transmitting node. The nodes of such a neighborhood are said to be located within one “hop” of the transmitting node. In FIG. 1, for example, nodes N1, N3, N4, N5, N6, N7 and N8 are members of the neighborhood surrounding node N1.
Nodes N2, N9, N10, N11 and N12 are each located two hops away from node N1 and node N13 can be said to be three hops away from node N1. When data transmitted from node N1 is to be propagated multiple hops, the data must be relayed by one or more of node N1's neighbors. For example, data transmitted by node N1 can be relayed by its neighbor node N8 to a node such as node N12 that is located two hops from node N1.
Receivers are generally capable of processing only one transmission at a time. Simultaneous transmissions, also known as collisions, contentions or conflicts, can be avoided by assigning a specific transmission time slot to each communicating node. Several approaches have been developed for assigning slots to nodes. The approach chosen for a particular application is generally a consequence of the type of network application (broadcast, multicast, unicast, datagrams, virtual circuits, etc.) at issue. Since the problem of optimally assigning slots is mathematically intractable, a heuristic approach has been applied. This approach resulted in the development of an integrated protocol that both chooses the number of slots to assign to each neighboring node and coordinates their activation in the network.
Many applications require self-organizing, wireless networks that can operate in dynamic environments and provide peer-to-peer, multi-hop, multi-media communications. Key to this technology is the ability of neighboring nodes to transmit without interference. Neighboring nodes transmit without interference by choosing time slots and channels that do not cause collisions at the intended unicast or multicast receivers. The Unifying Slot Assignment Protocol (USAP), which is disclosed in U.S. Pat. No. 5,719,868, provides a protocol establishing such a communication system. USAP is a dynamic assignment protocol that monitors the RF environment and allocates the channel resources on demand. It automatically detects and resolves contention between nodes for time slots, such contention arising for example from changes in connectivity. The specification of U.S. Pat. No. 5,719,868, issued Feb. 17, 1998, is hereby incorporated herein by reference, including all drawings and appendices.
In certain applications, however, it is desirable or necessary to establish a network including nodes that do not participate in a dynamic assignment protocol alongside nodes that do use a dynamic assignment protocol. Such a system would permit nodes to be included in the network that are not capable of participating in the dynamic assignment protocol used by the network. For instance, nodes using older technology or nodes having insufficient computing resources could be integrated with the network. In addition, such a method could be used to help guarantee adequate channel capacity to a node deemed critical to network operation.
Consequently, there exists a need for a dynamic assignment communication system capable of including nodes that do not directly participate in the dynamic assignment protocol.